Big brake upgrade!

Sourcing the parts (August ’18)

Just picked up some big brakes for the old girl! i know that buying brakes for a non-running car is an odd choice…but you don’t find a lot of 90s BMWs around any more. I drove out to pull them myself, met a few really nice scrappers, had an all-around good day in fact. It’s a shame this car was scrapped. Engine seemed healthy so I’d presume a dead transmission or an abandoned car. Check out how well preserved those tools are!

Installing the parts

After a little cleaning & lubing, I installed the components today. As advertised, the larger calipers on the 540i 740i are a direct fit. Be sure to grab the carriers as well when you find a set, and you might as well take the front rotors if they look OK. The 740i rear rotor won’t fit, so I left them at the salvage yard and ordered a new set of rear rotors from the ’94-95 E34 540i. I also opted to install a spare set of E24 M6 front rotors, since they’re a bit worn and not really worth selling. The M6 rotors are internally vented and slightly lighter. IMHO a good choice.

Front set ready to go

Here’s the stock E28 brake.

E32 740i rotor weighs 15.5#.

E24 M6 rotor weighs almost 17#.

Here’s the 740i front caliper, 13# with hose.

Stock E24 front rotor, just over 12#.

Stock vs. M6 sizes.

You can see how much larger the M6 part is here.

Stock E24 front caliper is 11#.

I know it’s rusty, but it’s installed!

Stock rear E24 setup. Solid rotor.

740i rear caliper on the left, E24 on the right

Massive upgrade!

E34 540i rear rotor is nearly 13#.

E24 rear rotor is only 9#.

740i rear caliper, carrier & pads come in at 7.5#.

635CSi rear caliper, carrier & pads are only 6#.

Was it worthwhile? I’m told it is, although my lower back grumpily disagrees. I’ll update this page once I get the system purged & bled.

I was curious about how much the E23 540i setup increases sprung weight so I also carefully weighed everything as I did this job. Per each side, the E34 540i front caliper is 13#, E24 M6 rotor is 17#; total weight is 30#. Stock E24 is 23#, so the upgraded front setup is about 30% heavier than the stock E24 setup. The E34 540i rear caliper is 7.5#, rotor is 13#; total weight is 20.5#. Stock is 15#, so the upgraded rear setup is about 33% heavier than the stock E24 setup. We’re also required to run 16″ wheels to clear these larger front brake, so we gain a good bit of sprung weight there as well.